Males from a mating of wild mice, Mus musculus, and certain inbred strains of the laboratory mice are sterile, while females are fertile. One of the genes controlling this male sterility, the Hybrid sterility-1 (Hst-1) gene, maps to mouse chromosome 17, to the region occupied by the t complex. The overall goal of the project is to clone the Hst-1 gene and its human homologue. A high-resolution map of the Hst-1 region will be constructed by typing appropriate backcross animals and by mapping with recombinant t haplotypes. DNA markers nearest to the Hst-1 gene will be obtained by screening a band-specific chromosome 17 library and a mouse genomic YAC library. The selected clones -will be mapped and ordered by a combination of methods involving molecular and classical genetics. All coding sequences on the DNA fragment(s) carrying the Hst-1 gene will be identified, primarily by the exon-trapping method and tested for their expression in the testes. The one (or few) testes-expressed genes will be sequenced in an effort to find polymorphism correlating with the Hst-1 alleles. The putative candidate(s) for the Hst-1 gene will be identified definitively by targeted replacement of the endogenous Hst-1 gene in embryonic cells. The mouse Hst-1 probes will be used to screen human genomic libraries and the human homologue of Hst-1 will be isolated and sequenced . The chromosomal location of the putative human HST-1 gene will be determined by in situ hybridization. Cloning of the human gene would provide a unique opportunity to examine its possible association with hereditary infertility and to study the causes of human infertility at the molecular level. The proposed research is a collaborative project between two groups, one at the University of Miami and the other at the Czechoslovak Academy of Sciences in Prague.